Bug 851785. Stop expecting the image to be decoded in async_load_tests.js because it never does anything that would require a decode to happen. r=joe
Bug 851785. Stop RasterImage::FrameRect from initiating a decode. r=joe

imgStatusTracker::SyncNotify is the only caller and it does not need a decode to be initiated.

This prevents us from kicking off a decode for almost every image we download.